1. Field of the Invention
The present invention generally relates to a passive device, in particular, to a choke.
2. Description of Related Art
A choke functions to stabilize a current in a circuit and achieve the effect of filtering noises. The function of the choke is similar to that of a capacitor, i.e., both for regulating the stability of the current by storing and releasing electric energy in the circuit. Compared with the capacitor that stores electric energy in the form of an electric field (charges), the choke achieves the same purpose in the form of a magnetic field.
FIG. 1 is a schematic top view of a conventional choke. Referring to FIG. 1, the conventional choke 100 has a toroidal core 110 and a wire 120 wound around the toroidal core 110. A fabrication method of the choke 100 is described as follows. First, a magnetic powder (not shown) is press-fit into the toroidal core 110. Then, the toroidal core 110 is fired at a temperature above 600° C. Afterwards, the wire 120 is wound around the toroidal core 110 manually. As the choke 100 needs to be produced by winding the wire 120 on the toroidal core 110 manually instead of being produced automatically, the manufacturing process of the choke 100 requires a considerable labor cost.
Another type of choke is a combined choke, in which a combined core is assembled by an adhesive. However, if the control of the amount of the adhesive is undesirable or the surface of an assembling face of the core is uneven in the assembly, the thickness of the adhesive after the assembly may easily become non-uniform, thus resulting in a large inductance value variation of the choke and obtaining a low yield. In order to solve the above problem, a special surface treatment procedure is proposed for enhancing the assembly precision and enlarging the assembling face of the core, but the manufacturing cost of the choke is increased accordingly.